DE2400043A1 - IMPROVED METHOD FOR BULK POLYMERIZATION OF ACRYLIC NITRILE - Google Patents

Description

Dipl,! Ng.P.WIRTH Dr. V. SCH MIED-KOWARZIK Dlpl-lng. G. DAN NENBERG Dr. P. WEINHOLD Dr. D. GUDEL

281134 β FRANKFURTAM MAIN

TELEPHONE (0611) GR. ESCHENHEIMER STRASSE 30

SK / SK case no. MF. 1799

Montedison Fiber SpA Via PoIa 14
Milan / Italy

Improved Process for the Bulk Polymerization of Acrylonitrile

The present invention relates to an improved method for Bulk polymerization of acrylonitrile alone or in a mixture with other ethylenically unsaturated monomers copolymerizable with acrylonitrile. - "■.

It is known that the bulk polymerization of acrylonitrile can be regulated under Temperature conditions and in a flowable polymerization medium only under special working conditions are carried out; these are essentially

a) Polymerization of acrylonitrile alone or in a mixture with up to 50 Mol- $ at least one other, copolymerizable, ethylenically unsaturated Compound by a continuous or semi-continuous polymerization process;

b) Use of a radical catalyst system with a decomposition constant (Kd) over 1 h "¹;

c) Use of a reaction or residence time of at least sufficient Time to allow half of the catalyst to decompose;

409827 / 10-1

«■ fa <m *

d) Use of a catalyst concentration of at least the same 2.ID "^. Q. Mol / l, where Q is the reaction or residence time in hours.

As radical catalysts with a high decomposition constant, catalytic Systems made from an organic hydroperoxide, an oxidizable sulfoxy compound or sulfur dioxide and a nucleophilic compound such as water, methyl alcohol, ethyl alcohol and higher alcohols have been proposed. as Organic hydroperoxides can advantageously be used cumene hydroperoxide, tert-butyl hydroperoxide or cyclohexanone hydroperoxide.

Other catalyst systems suggested for such a polymerization are: an organic hydroperoxide and a monoester of sulphurous acid according to

of the following general formula O

(R ₁ - OS - O) _n Me

in which R> represents an alkyl, cycloalkyl, aryl or alkylaryl group 1-12 carbon atoms, Me a metal of the first or second group of the periodic system or ammonium or aluminum, and η means one Has a value of 1, 2 or 3, depending on the valence of Me; or a organic hydroperoxide, a magnesium alcoholate and a dialkyl sulfate

general formula 0

R ₂ -OSOR ₃

in which Rp and R ", which can be the same or different, for a simple one or substituted, linear or branched alkyl radical or a cycloalkyl radical having 1-12 carbon atoms.

It is known that - as is generally the case in all polymerizations - the molecular weight of the polymer obtained is regulated by varying the concentration of the catalyst used. This method for However, regulation of the molecular weight of the polymer has disadvantages if one of the abovementioned systems is used as the catalyst.

09827/1041

Varying the concentration of these catalysts doesn't just make one A change in the molecular weight of the polymer is achieved, but also a modification of the coloring properties of the same in the sense that when it is increased the catalyst concentration to reduce the molecular weight of the polymer at the same time an increase in the acid end groups, expressed as equivalent / g polymer, is achieved which are bound to the polymeric chain.

All of the above-mentioned processes have disadvantages when the polymer is used for production fibers, filaments or films in which good coloring properties are required is intended.

For these purposes it is advantageous to use the molecular weight of the polymer while keeping the dyeing properties constant, i.e. by keeping the acid end groups constant.

To reduce the molecular weight of the polymer without changing the As is known, suitable transfer agents, such as mercapto compounds, are added to the polymerization medium with the acid group content. These connections .show, however, in one with a catalyst system based on one of the above mentioned organic hydroperoxide initiated polymerization only a very limited effect, as can be seen from the following table

Table 1

2-r-mercaptoethanol Average numerical molecular weight ppm 'of the polymer

4-5 000 500 k5 400

1 000 ¥ f 800

2,000 42,000

3,000 kO, 000

The results shown in Table 1 were obtained by continuous

Polymerization of a mixture of 82 wt .- ^ acrylonitrile and 18 # vinyl acetate with a water content of 0.3 % at V) ⁰ C. and with a contact time of

409827/1041

30 minutes in the presence of 0.25 % cumene hydroperoxide and 0.5 $ SO ₂ , all percentages being expressed in terms of weight, based on the monomer mixture.

The average numerical molecular weight of the polymer (PM) is determined by the intrinsic viscosity pn J, expressed in dl / g, according to the following equation

0.75 ₍₁₎ -

the structural viscosity äts number [/ η J is measured at 25 ° C. in dimethylformamide.

It has now been found that in the bulk polymerization of acrylonitrile under the above-mentioned polymerization conditions and by using a catalyst system based on an organic hydroperoxide of the type specified, a surprising chain transfer effect is achieved if the polymerization is carried out in the presence of a mercapto compound and a basic nitrogen containing compound in amounts not exceeding 2 % _t based on the monomer.

The combined effect of the mercapto compound and the basic, nitrogen-containing Compound in the bulk polymerization of acrylonitrile under the conditions given above must be regarded as surprising when one considers that the mercapto compounds alone have almost no effect, as shown in Table 1, while the basic nitrogen-containing compound not only does not act as a chain transfer agent, but even causes an increase in the molecular weight of the polymer, as shown in the following Table clearly shows in which as a basic, nitrogen-containing compound Dimethylacetamide is used.

409827/1041

- 5 Table 2

Gew .- # Dimethylacetamidkonzen- average numerical molecular tration, based on the monomer weight of the polymer

45,000

, 0.04 50,000

0.08. 66,000

• 0.16 68,000

0.32 86,000

0.6 *) - 110,000

The polymerization conditions were the same as for Table 1 and that average, numerical molecular weight of the polymer x * ar by the Structural viscosity has been determined according to equation (I).

The following table 3 shows the surprising effect of the chain transfer by using the two types of connections mentioned above together.

■ Table 3

ppm 2-mercapto wt .- $ DimetiSjOacetamid, avg. numerical ethanol. ppm or more autonomous, Govt. t mole weight d. receive .polymerisates

-. - 45,000

500 0.08 43,000

1,000 0.08 25,000

500 0.16 42,000

1,000 0.16 15,000

1,000 0.64 12,000

1 000 1.0 10 000

The polymerization took place under the conditions given above, and that average numerical molecular weight of the polymer was through the The structural viscosity number is determined according to equation (1).

409827/1041

- ο -

Of the general formula R ^ -SH, any compound can be used as a mercapto compound, in which R ^. for a linear / or branched aliphatic

possibly

see radical with 1-20 carbon atoms, the / an -OH or -SH group in the chain contains. These include the following compounds: n-propyl mercaptan, n-butyl mercaptan, n-octyl mercaptan, n-decyl mercaptan, n-dodecyl mercaptan, n-hexadecyl mercaptan, 2-mercaptoethanol, 3-mercaptopropanol, etc., Athandithiol, propanedithiol etc.

The mercapto compounds in which R ^ is a linear or branched one Alkyl radicals having 2-12 carbon atoms are preferred in practice. These compounds are mixed into the polymerization medium in amounts not exceeding 3000 ppm, with amounts between 500-1500 ppm giving best results deliver.

As the basic nitrogen-containing compound, an amide of the following general Formula can be used:

R ₅ -CO-N ' ⁶ (2)

in which R ₁ -, R 1 - and R ", which can be identical or different, stand for hydrogen or an alkyl radical with 1-6 carbon atoms. Of these compounds, dimethylformamide and dimethylacetamide are preferred. In practice, one of the two amides is expediently used, depending on the type of solvent used in the subsequent spinning stage of the polymer obtained. That is to say, if dimethylacetamide is used as the spinning solvent, the polymerisation is expediently carried out in the presence of small amounts of this amide.

Instead of the amides of the above general formula (2) one can also use aliphatic, cycloaliphatic or aromatic, primary, secondary or tertiary

409827/1041

Amines, such as triethylamine, tributylarain, dimethylamine, cyclohexylamine, pyridine etc., use.

The amount of the basic, nitrogen-containing compound is usually below 2% by weight , based on the monomer or the monomer mixture} it is preferably about 0.1-1% by weight. _r

It should be noted that at such concentrations the compounds used as spinning solutions for acrylic polymers generally do not have any have a solubilizing or softening effect. As is well known, must for such an effect is the concentration of the compound acting as a solvent be over $ 2 <.

The polymerization can be continuous or semi-continuous at one Temperature between room temperature and the boiling point of the or the Monomers are carried out. The selected polymerization temperature is in the usual way, e.g. by immersing the reactor in a thermally regulated Bath or by circulating a coolant around the walls or in lines inside the reactor as well as by removing the heat of reaction internal evaporation of the reaction medium, regulated.

It is advisable to carry out the polymerization in the absence of oxygen, which has an inhibiting effect on the polymerization.

As ethylenically unsaturated monomers copolymerizable with acrylonitrile, can be named: alkyl, aryl and cycloalkyl acrylates, such as methyl acrylate, Ethyl acrylate, isobutyl acrylate, etc .; the alkyl, aryl and cycloalkyl methacrylates, such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, etc .; U.N-

saturated ^ ketones; Vinyl esters such as vinyl acetate, vinyl propionate, etc .; Styrene and its alkyl derivatives, vinyl chloride or vinylidene chloride, vinyl fluoride,

409827/10 41

- 8 vinyl and vinylidene bromide, - methacrylonitrile, butadiene, etc.

The process according to the invention enables both the desired coloring properties Achieve regardless of the molecular weight of the polymer and significantly improve the flowability of the polymerization mass, such as from the following table 4 emerges. ''

The results cited there refer to the polymerization of a mixture of 82 $ acrylonitrile and 18 p vinyl acetate with a water content of 0.3 wt .- ^ in the presence of 0.5 wt .- ¹ ^ SO ₂ and with different amounts of cumene hydroperoxide according to Information in the table. The residence time of the monomers in the reactor was 30 minutes and the polymerization temperature was 45.degree. However, the percentages by weight given relate to the monomer mixture.

Dimethyl
acetamide Table 4 average Sulfone viscosity - 2-mercapto num. mol. weight
d.Polymer groups d.Polymer,
medium; poises Concentration of - ethanol; ppm 120,000 15th 6.5 Cumene hydro
peroxide - 71,000 19.5 3.2 0.05 0.08 __ 45,000 33 2.0 0.10 0.08 - 43,000 33 0.6 0.25 0.64 500 25,000 33 0.1 , 0.25 1,000 12,000 33 0.05 0.25 1,000 0.25

The sulfonic groups are expressed in milliequivalents per kg of polymer and were determined in a solution of 1 wt .- ^ polymer in dimethylformamide.

This solution was passed through an ion exchange column, the ■ two 'Equal and separate amounts of rAmberlite IR 120 (kaionic resin) in the upper Part and Amberlite IR 410 (anionic resin) in the lower part. the The column had a height of 50 cm and an inner diameter of 1.9 cm.

409827/1041

The sulfonic acid groups of the polymer were titrated directly in Dimethylformamide solution with a methanol solution of a basic, quaternary Ammonium containing compound. The titration was carried out potentiome «. tric by a platinum electrode.

■ The polymers or copolymers obtained by the process according to the invention show a high bulk density and improved chemical and physical properties. The polymers or copolymers are also suitable for conversion into fibers with improved properties of whiteness and thermal stability.

The following examples illustrate the present invention without it to restrict.

Example 1

Was pre-filled into a container provided with a stirrer, thermometer and overflow pipe 2500 cc Polymerisatiensieaktor, the on half its volume with a mixture of 82 $ and 18% vinyl acetate (water content of the mixture = 0.3 i>) and heated to 45 C, were continuously introduced:

g / h

Cumene hydroperoxide 8.0

gaseous SOp 20

Dimethylacetamide 3.2

2-44captoethanol 4.0

After the first 10 minutes, the monomer mixture was introduced at a rate of 4000 g / h o The polymer conversion was 44 %. The under steady state conditions, d _"o h after 2.5 hours, collected polymer was filtered, washed with water and 24 hours at 60 ° C. dried and showed the following properties:

409827/1041

2400043 ι, 3 dl / g 30th ο, 52 g / cc 7, _r ip = 99.2

Structural viscosity number

Sulphone groups in milliequivalents / kg polymer bulk density
copolymerized vinyl acetate

Color of the polymer .

AB = 96.0

The color was measured using a General Electric spectrophotometer integrator according to the C.I.E. Measurement and display system of colors measured.

According to this system, the color is recorded as a purity index (IP) and as a brightness (B) * in each case based on standard lighting in the form of an emission source corresponding to a black body heated to 6300 K, expressed.

If the polymerization takes place under the above conditions in the absence of Dimethylacetamide and 2-mercaptoethanol, then a copolymer was obtained with an intrinsic viscosity of 1.6 dl / g, with 30 milliequivalents Sulphonic acid groups per kg of polymer and a color of IP = 98.8 and .. B = 95.0

Example 2

According to Example 1, a 2.5-1 reactor, which was prefilled to half its volume with a mixture of 82 $ acrylonitrile and 18 % vinyl acetate, was continuously charged with the following materials:

Cumo.l hydroperoxide 10 g / h

gaseous SO2 20 g / h Dimethylacetamide 2.96 g / hr

Ethanedithiol 2 g / hour

The polymerization conversion was h2 $ and the copolymer obtained in this way showed the following properties:

Structural co st itäs number 1.1 dl / g

Sulphone groups in milliequivalents / kg polymer 32

Bulk density 0.5 g / ccm

copolymerized vinyl acetate 7.4 %

409827 / 1CH1

B = 95.9

example 3

Under the conditions and with the amounts of Example 2, but using 2.4 g / h of n-butyl mercaptan instead of 2 g / h of ethanedithiol, a conversion of 43 $> was achieved, the copolymer exhibiting the following properties:
Structural viscosity number

SuIf on groups in milliequivalents / kg polymer bulk density

copolymerized vinyl acetate Color of the polymer

Example 4

1.2 dl / g 33 o, 5l g / ccm 7.3 rip = 99.1 Ib = 96.2

In the process of Example 2, instead of the 2 g / h ethanedithiol, 5 g / h n-dodecyl mercaptan is used, and a polymerization conversion is achieved from 43 # ,. the resulting copolymer having the following properties showed:

Structural viscosity 1.2 dl / g

SuIfon groups in milliequivalents / kg Polymsrisat 32

Bulk density 0.49 g / ccm

copolymerized vinyl acetate 7.4 #

{TP = OO 1 B = 96.1

Example £

Under the conditions of Example 1, the following materials became continuous introduced into the reactor:

Cumene hydroperoxide 10 g / h

gaseous SO ₂ 20 g / h

Dimethylformamide 2.4 g / hour

2-mercaptoethanol 2 g / h

4098277 1041

The polymerization conversion was 42. # and the copolymer had the following properties:

Structural viscosity number 1.1 dl / g

SuIf on groups in in milliequivalents / kg polymer 32

Bulk density 0.5 g / ccm

Color of the polymer * ■ /! ¥ - 99fO

¹ B = 96.0

Example 6

Under the conditions mentioned in Example 1, the following materials were introduced into a reactor which had previously been pre-filled to half its volume with a mixture of 91 $ acrylonitrile and 9 $ methyl acrylate (water content of the mixture = 0.3 V and adjusted to 40 ° G, was heated:

Cumene hydroperoxide 10 g / hour

gaseous SO ₂ 20 g / h

Dimethylacetamide 3.2 g / h

2-mercaptoethanol. 4 g / h

The polymerization conversion was 47.5% and the copolymer obtained in this way showed the following characteristics:

Intrinsic viscosity - 1.3 dl / g

Sulfon groups in milliequivalents / kg polymer 33

Bulk density 0.52 g / ccm

copolymer-based methyl acrylate 7 »44 #

Color of the polymer T ~ "" · - *

^L B = 96.2

Example 7

Under the conditions mentioned in Example 1, the following materials were continuously introduced into a reactor which was prefilled with acrylonitrile to half its volume and ^{heated to 40 °} C.:

409827/1041

Cumene hydroperoxide 10 g / hour

gaseous SOg 120 g / h Dimethylacetamide 3.2 g / h

2-mercaptoethanol 8.0 g / hour

After the first 10 minutes, the acrylonitrile was at a flow rate • speed of 4000 g / h introduced into the reactor. The polymerization conversion was $ 54.6, the polymer obtained in this way showed the following properties:

Structural viscosity number 2.0 dl / g

Sulphone groups in milliequivalents / kg polymer 24

Bulk density 0.48 g / ccm

Color of the polymer J IP = 99.0

B = 95.0

Example 8

Under the conditions mentioned in Example 1 with the same monomer mixture the following materials were introduced into the reactor:

Cumene hydroperoxide 7.2 g / hr

10% sodium methyl sulfite solution in methyl alcohol% ecm dimethylacetamide 1.92 g / h

2-mercaptoethanol 6 g / h

After the first 10 minutes, the monomer mixture was added to the reactor at an introduction rate of 24C0 · g / hr. The polymerization conversion was $ 50.6, and the copolymer thus obtained showed the following Characteristics:

Structural viscosity number. 1.5 dl / g

Sulphone groups in milliequivalents / kg polymer 23

Bulk density 0.59 g / ccm

f IP = 99.0 B = 96.0

Color of the polymer ->

VR

09827/1041

Claims (1)

- 14 claims I Ij- Process for the bulk polymerization of acrylonitrile alone or in a mixture with up to 50 mol $ of at least one other ethylenically unsaturated compound copolymerizable therewith, in which a) the polymerization is carried out continuously or semi-continuously will;' b) a free radical catalyst system with a decomposition constant (Kd) over 1 hour from the group of organic hydroperoxides, oxidizable sulfoxy compounds or sulfur dioxide and a nucleophilic compound} organic Hydro ^ peroxides and a monoester of sulphurous acid; and inorganic Hydroperoxides, magnesium alcoholate and a dialkyl sulfite of the above Kind is used; c) such a reaction or residence time is used that is at least Sufficient for half the decomposition of the catalyst; and satorsystems _3 d) a concentration of the radical catalyst of at least 2.10. Q moles / l is used, where Q is the reaction or residence time in hours, and wherein the polymerization is carried out in the presence of a mercapto compound, characterized in that the Polymerization medium furthermore a basic nitrogen-containing compound in an amount not exceeding $ 2 based on the monomer. 2. - Method according to claim 1, characterized in that a mercapto compound the general formula: is used in which R ^ for a linear or branched aliphatic Radical with 1-20 carbon atoms and optionally an OH or -SH group in the chain. 409827/1041 3 · - method according to claim 2, characterized in that R ^ for an ali phatic radical with 2-12 carbon atoms. 4. Process according to Claims 1 to 3, characterized in that the amount of mercapto compound added to the polymerization medium is below 3000 ppm "and preferably between 500-1500 ppm. 5 · - Method according to claim 1 to 4, characterized in that as basic Nitrogen-containing compound is an amide of the general formula is used in which R-, R ^ - and R ", which are the same or different can represent hydrogen or an alkyl radical having 1-6 carbon atoms. 60- method according to claim 5 »characterized in that as basic Nitrogen containing compound dimethylformamide or dimethylacetamide is used. 7.- The method according to claim 1 to 4, characterized in that the basic .Nitrogen-containing compound an aliphatic, cycloaliphatic or aromatic, primary, secondary or tertiary amine is used. 8.- The method according to claim 1 to 7 _f, characterized in that the amount of basic nitrogen-containing compound between 0.1-1 wt .- $, based on the monomer or the monomer mixture is. 9e method according to claim 1 to 8, characterized in that the polymerization temperature is between room temperature and the boiling point of the monomer or monomer mixture. The patent attorney: 409827/1041